Athanasius of Alexandria (298?–373) was a key figure in the in the life and theology of the fourth-century Church. In most of the contemporary controversies and events his force of personality made an indelible mark on developments and influenced their direction and movement to a remarkable degree. Although known most widely for his defense of the communion of being of the Son incarnate in Jesus with the Father, he was no less important in the incipient controversies concerning the divinity of the Holy Spirit. At a decisive hour of the Church's life, Athanasius not only secured her faith in the one Godhead of Father and Son; he delineated the lines upon which her pneumatological doctrine was to develop. With his characteristic single-mindedness, and by constant reiteration of certain propositions, Athanasius laid down the general lines of the future development of the doctrine, thus making the question of the divinity of the Holy Spirit as fundamental a part of the Church's consciousness as the doctrine of the Son's full divinity had become through his disputes with the Arians.